1) Test cases with test data exactly as the input boundaries of input domain . values 1 and 1000 in our case.
2) Test data with values just below the extreme edges of input domains . values 0 and 999.
3) Test data with values just above the extreme edges of input domain . values 2 and 1001.
Boundary value analysis is often called as a part of stress and negative testing.
Note: There is no hard-and-fast rule to test only one value from each equivalence class you created for input domains. You can select multiple valid and invalid values from each equivalence class according to your needs and previous judgments.